First of all I think you win the award for most interesting (non-pen related) question for a while!
I think what Ian says sounds like good advice, and if you don’t have a pyrography machine you could at least test the theory by heating a scalpel (or similar) and seeing if you can use it to seal a small area. (A candle is always handy to have on hand for this sort of thing).
If that works then the pyrography machine route would be the way to go, as it will offer you the option to regulate the amount of heat being applied.
In any case I’d be interested to hear if you do find a solution that works and how you get on.
Cheers
Ash
